(a) Field of the Invention
The present invention relates to an apparatus and a method for allocating uplink resources for transmission of uplink data.
(b) Description of the Related Art
In accordance with an increase in Internet users using a mobile communication system, mobile communications carriers are seeking an efficient method for increasing capacity of the mobile communication system. The most efficient and intuitive method for increasing capacity of the mobile communication system is to increase a bandwidth by additionally securing a frequency of a licensed band for the mobile communication system. The mobile communication carrier may efficiently provide a mobile communication service by exclusively using the secured licensed band frequency, but there is a disadvantage that it costs a lot to license and use the frequency of the licensed band, and the frequency of the licensed band allocated for the mobile communication system is limited. Accordingly, a method for providing the mobile communication system using a frequency of an unlicensed band, a frequency of a TV white space (TVWS), or a frequency of a licensed/unlicensed band (hereinafter, referred to as ‘an unlicensed band’) shared by the mobile communication carriers in which a lot of relatively available frequency bands exist and costs are also inexpensive has been considered
A communication system using the frequency of the unlicensed band has the following limits.
First, in order to minimize an influence on another system sharing the unlicensed band, transmission power is limited. Therefore, in the case in which a licensed band system and an unlicensed band system are deployed on the same place, a coverage hole may occur in the unlicensed band system, unlike the licensed band system.
In addition, for a fair coexisting with a neighboring unlicensed band system, the frequency of the unlicensed band should be discontinuously or randomly used. As a result, transmission reliability of a control channel, a common channel, and the like used in the mobile communication system may be decreased. Further, a regulation on the frequency of the unlicensed band should be obeyed.
For example, in order to transmit data, a system using the unlicensed band may perform a clear channel assessment (CCA) to search a channel in frequency resources and determine whether or not the channel is used depending on the result of CCA, and even though a specific device occupies the channel depending on the result of CCA, a channel occupancy time may be limited according to a frequency regulation. Further, the specific device may not occupy the channel during a time exceeding a maximum channel occupancy time, and needs to additionally perform the CCA in order to re-occupy the channel.
Due to the limit of the unlicensed band system described above, rather than a standalone system that uses only the unlicensed band, a scenario in which the unlicensed band supplements mutually with the licensed band system has been examined. In this scenario, control functions that require reliability such as a terminal control, a mobility management, and the like are performed in the licensed band, and traffic functions such as an increase in wireless transmission speed, a wireless traffic load distribution, and the like may be supplemented by the unlicensed band system.
That is, the system or carrier operated in the licensed band performs the control and traffic functions, and the system or carrier operated in the unlicensed band frequency performs the traffic function. The above-mentioned operation may be implemented by a carrier aggregation (CA) technology. For example, examples of a CA configuration of 3GPP LTE include a CA between an FDD carrier of the unlicensed band and a carrier of the licensed band (i.e., LTE), a TDD carrier of the unlicensed band in which both uplink/downlink are operated and a carrier of the licensed band, and the like.
The cellular system using the unlicensed band has an advantage that it may provide the mobile communication service of which service quality is guaranteed by utilizing inexpensive and rich frequency resources and an advanced interference control technology. However, in order to secure the above-mentioned advantages while conforming to a variety of regulations of the unlicensed band and coexisting with other unlicensed band systems, new coexistence technology and interference control technology are required. Particularly, due to characteristics of the unlicensed band, the device operated in the unlicensed band occupies/uses the channel, and in this case, in the case in which the carrier aggregation technology is applied, the carrier aggregation technology that considers characteristics of the licensed band and the unlicensed band, and an operation method thereof are required. In addition, by reflecting limits (characteristics) for operating the device of the unlicensed band, a reliable wireless transmission service equivalent to an existing cellular system should be provided.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.